Low Temperature Measurements of Novel LowDimensional Systems

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Low Temperature Measurements of Novel
Low-Dimensional Systems

• James R. Maloney
• James M. Stock

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What Are Low Temperatures?
Room Temperature 300 K
Freezing Point of Water 273 K
Liquid Nitrogen 77 K
Liquid Helium 4 K
Our Sample 1.5 K
Absolute Zero 0 K
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So What are Low-Dimensional Systems?

• 1-D Chains
• 2-D Planes

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How Can This Make the World A Better Place?

• We want better high temperature superconductors
• High temperature superconductors have similar
  characteristics to low-dimensional
  systems
• If were going to make progress, we need to
  understand these systems!

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Outline

• I. Reaching Low Temperatures
• II. Our Samples
• III. Properties Under Investigation
• IV. Results

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I. Reaching Low Temperatures

• Designed a cell compatible with a cryogenic probe
  to house our samples
• The probe could be chilled by liquid nitrogen,
  liquid helium, and evaporative cooling

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The Sample Cell
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The Cryogenic Probe
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Bridge Balancing Method
Capacitance Bridge
Lock-In Amplifier
Signal Generator (Internal)
Sample
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II. Our Samples

• (CH3)2NH2CuCl3 MCCL

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II. Our Samples

• Langmuir-Blodgett (LB) film

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III. Properties Under Investigation

• Search for phase transitions of MCCL
• By observing capacitance
• Look at the conductivity of LB film
• Measuring conductance from the capacitance signal

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IV. Results

• MCCL

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IV. Results

• LB film

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IV. Results

• Aluminum

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What Is Next?

• Reproducibility of 154 K MCCL transition
• Search for second phase transition surrounding 10
  K
• Investigate possible noise coupling between
  cavities

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Questions?